Cass Sunstein, administrator of the powerful Office of Information and Regulatory Affairs in the White House Office of Management and Budget, will return later this month to his previous post at Harvard Law School, the White House will announce Friday.

Sunstein, a celebrity academic who met Barack Obama when they were both teaching at University of Chicago Law School was among the world’s most-quoted law professors when he came to Washington in 2009. He was named the new president’s chief regulatory enforcer (often called the “regulatory czar”) as head of OIRA, “oh-eye-ruh,” an office that gets little attention but is among an administration’s most potent levers.

Like Obama, Sunstein embraces “behavioral economics” – an emphasis on human behavior, rather than abstract theory, for identifying incentives to promote desired financial and environmental activity by individuals and corporations. The field of study supplied early underpinnings for Obama’s plans for health care and financial regulation.

Sunstein became a lightning rod for liberal activists who had hoped the administration would be more aggressive with regulatory policy. He had met his future wife – Samantha Power, who also works for the White House as the National Security Council’s Senior Director for Multilateral Affairs and Human Rights — while the two were campaigning for Obama in Iowa.

At Harvard, Sunstein will be Felix Frankfurter Professor of Law and Director of the Program on Behavioral Economics and Public Policy.

The president said in a statement: “For the last three and a half years, Cass Sunstein has helped drive a series of historic accomplishments on behalf of the American people. From putting in place lifesaving protections for America’s families, to eliminating tens of millions of hours of paperwork burdens for our nation’s citizens and businesses, Cass has shown that it is possible to support economic growth without sacrificing health, safety, and the environment.

“Cass has shepherded our review of existing rules to get rid of those that cost too much or no longer make sense, an effort that is already on track to save billions of dollars. With these reforms and his tenacious promotion of cost-benefit analysis, his efforts will benefit Americans for years to come. I can’t thank him enough for his friendship and for his years of exceptional service.”

Jeffrey Zients, acting Obama director, will miss tossing a football around with Cass in the halls of the Eisenhower Executive Office Building.

“With regret and deep gratitude, I am announcing that Office of Information and Regulatory Affairs Administrator Cass Sunstein will be leaving OMB this month,” Zients said in a statement. “Having served in the Administration since the very start, and with the recent birth of a baby daughter and the coming of the new school year, Cass will be rejoining Harvard Law School … “We are grateful to Cass for his years of public service and for his leadership and dedication in assisting the President in overseeing the nation's regulatory program. Among other things, his emphasis on transparency and on innovative, low-cost regulatory tools contributed to the Administration's Open Government Initiative; to numerous efforts to promote clear, simple disclosure to inform consumers and investors; and to creative reforms to increase public participation in the regulatory process and to promote accountability to the American public.

“Cass also oversaw the historic government-wide regulatory ‘lookback,’ designed to streamline, improve, and sometimes eliminate existing rules — helping businesses, consumers, and workers alike. That effort has already produced over $10 billion in five-year savings, along with the elimination of tens of millions of hours in annual paperwork burdens. Because the lookback has been institutionalized, and made a regular feature of American government, far greater savings are expected over time. His leadership in promoting disciplined consideration of costs and benefits, and selection of the least costly alternative, helped generate, to date, well over $100 billion in net benefits.

“Cass has also played a leading role in the Administration's Smart Disclosure initiative, designed to use modern technologies to better inform consumers; in promoting consideration of cumulative burdens of rules; in recent efforts to simplify our regulatory system and to reduce reporting burdens; and in implementing the recommendations of the President's Jobs Council.

“He has also participated in the design of numerous rules that are, among other things, saving lives on the highways by making vehicles safer and reducing distracted driving; dramatically increasing the fuel economy of the nation’s cars and trucks; protecting public health by reducing air pollution; making our food supply safer; and protecting against discrimination on the basis of disability and sexual orientation. I can’t thank Cass enough for all he has done for OMB, for the Administration, and for the American people.”